Abstract
Exposing cells to excess metal concentrations well beyond the cellular quota is a powerful tool for understanding the molecular mechanisms of metal homeostasis. Such improved understanding may enable bioengineering of organisms with improved nutrition and bioremediation capacity. We report here that Chlamydomonas reinhardtii can accumulate manganese (Mn) in proportion to extracellular supply, up to 30-fold greater than its typical quota and with remarkable tolerance. As visualized by X-ray fluorescence microscopy and nanoscale secondary ion MS (nanoSIMS), Mn largely co-localizes with phosphorus (P) and calcium (Ca), consistent with the Mn-accumulating site being an acidic vacuole, known as the acidocalcisome. VacuolarMnstores are accessible reserves that can be mobilized in Mn-deficient conditions to support algal growth. We noted that Mn accumulation depends on cellular polyphosphate (polyP) content, indicated by 1) a consistent failure of C. reinhardtii vtc1 mutant strains, which are deficient in polyphosphate synthesis, to accumulate Mn and 2) a drastic reduction of theMnstorage capacity in P-deficient cells. Rather surprisingly, X-ray absorption spectroscopy, EPR, and electron nuclear double resonance revealed that only little Mn2 β is stably complexed with polyP, indicating that polyP is not the final Mn ligand. We propose that polyPs are a critical component of Mn accumulation in Chlamydomonas by driving Mn relocation from the cytosol to acidocalcisomes. Within these structures, polyP may, in turn, escort vacuolar Mn to a number of storage ligands, including phosphate and phytate, and other, yet unidentified, compounds.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 17626-17641 |
| Number of pages | 16 |
| Journal | Journal of Biological Chemistry |
| Volume | 294 |
| Issue number | 46 |
| DOIs | |
| State | Published - Nov 15 2019 |
Funding
Acknowledgments—We acknowledge use of the Advanced Photon Source, a United States Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract DE-AC02-06CH11357. We thank Janice Pennington and Julio Paez Valencia for help handling samples and with the EDX analysis. Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource (SSRL). SSRL is a national user facility operated by Stanford University on behalf of the United States DOE, Office of Basic Energy Sciences. The SSRL Structural Molecular Biology Program is supported by the DOE, Office of Biological and Environmental Research, and by the National Institutes of Health, National Center for Research Resources, Biomedical Technology Program. Work at Lawrence Livermore National Laboratory was performed under the auspices of DOE Contract DE-AC52-07NA27344. Part of the research was performed at EMSL (Ringgold ID 130367), a DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research. This work was supported by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the United States Department of Energy (Grant DE-FG02-04ER15529). This work was also supported by DOE Genome Sciences Program Grant SCW1039 (to C. R., S. R. S., P. K. W., and J. P.), National Science Foundation Grant MCB1614965 (to M. S. O.), and National Institutes of Health Grants DK068139 (to T. L. S.), T32HL120833 (to B. E. L.) and GM 111097 (to B. M. H.). The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Cell Biology
